The device of this invention is used for plugging an opening in a panel and for supporting a member that is being passed through the panel usually in a vibration isolation and sealing mode. They are widely used in control panels and in panels separating various functioning parts of a machine. They find wide use in the automotive industry to position, support and seal various members such as wires, conduits, cables, rods or the like, which extend through the firewall or floor panel of the passenger compartment of the vehicle.
When an access hole in a panel is provided for assembly purpose or for tool access for attachment of other components to the panel, it has been common to use metal plug stampings for covering the holes, and these plugs can be fastened in various ways such as by the use of hot melt adhesives, by welding or brazing, or by the use of fasteners such as screws and the like.
When a grommet is used not only to seal the opening in the panel but also to sealingly pass a member through the panel, it has been common to fabricate the grommet with a metal insert embedded into an elastomeric body so that a portion of the insert can be deformed to hold the grommet to the panel while the elastomeric portion seals the grommet to the panel and also seals the member passing through the grommet to the grommet itself. Typical examples of this type of grommet are shown and described in U.S. Pat. Nos. 3,182,119 and 3,654,382.
U.S. Pat. Nos. 4,784,285 and 4,885,121 disclose a plug structure known as a dual durometer self-locking and sealing plug, and the method of making such a plug, respectively. While there is no teaching of the formation of a grommet which is the subject matter of the present invention, the molding methods of forming this plug are applicable to a grommet as well as a plug and serve as an improvement over molding methods shown and discussed in U.S. Pat. No. 4,081,879. U.S. Pat. No. 4,081,879 teaches the formation of a grommet or a plug which has an annular hard locking portion coupled with a softer sealing plastic portion which also serves as the panel opening covering. In U.S. Pat. Nos. 4,784,285 and 4,885,121, the method of forming the sealing plug includes the steps of, first, injection molding a harder annular locking portion and then injection molding the softer sealing portion in contact with the harder locking portion which remains in a portion of the injection mold. This sequential injection molding technique provides a preferred method of making the grommet of the present invention, although, sequential spraying or pouring into molds can be used as an alternative.
U.S. Pat. No. 4,081,879 presents an improvement over the composite metal and elastomeric grommets shown in U.S. Pat. Nos. 3,182,119 and 3,654,382. The principle of the '879 patent is embodied in the grommet of the present invention. The required strength and hardness that was supplied by the metal insert of the former grommets has been replaced by a plastic material having the requisite hardness to make the plug self-locking and resistant to dislodgement and impact, while also providing penetration resistance over the range of temperatures to which it is exposed. The sealing portion is made from a softer material which is chemically compatible with the hard material, having a requisite resilience to permit sufficient deformation when pressed against the inner periphery of the opening to facilitate insertion of the grommet into the opening and to provide the required sealing between the resilient peripheral portion and the inner peripheral portion of the panel as well as sealing the member being inserted through the panel. The hard locking and softer sealing plastic materials disclosed in the '879 patent are thermoplastic or thermosetting resins or mixtures thereof which can be cast as plastisols such as vinyl, and preferably a polyvinyl chloride. The grommet is formed by the sequential spraying method previously mentioned. The hard locking portion is an annular ring and the central, hole filling portion is a softer vinyl body portion which includes a flexible snout having a central opening to support the wire, rod or other member which extends through the panel opening. This snout has enough flexibility to yield or stretch and sealingly engage the member but the snout direction is fixed along the axis of the grommet. Thus the member must be pushed through the grommet at substantially a right angle to the panel, and skewing or misalignment makes the assembly difficult or impossible to accomplish. Also with the '879 grommet and the other prior art grommets discussed above, there can be no axial movement of the inserted member relative to the panel or periphery of the grommet after installation.